Compilare: main.cpp: In function 'int main()': main.cpp:16:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i <= s1.size(); ++i) ~~^~~~~~~~~~~~ main.cpp:18:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j <= s2.size(); ++j) ~~^~~~~~~~~~~~ main.cpp:20:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 1; i <= s1.size(); ++i) ~~^~~~~~~~~~~~ main.cpp:21:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 1; j <= s2.size(); ++j) ~~^~~~~~~~~~~~